1. Field of Invention
The invention relates to electrical connection boxes containing bus bars, particularly electrical boxes suitable for use in vehicles, for example automobiles.
2. Description of the Related Art
U.S. Pat. No. 5,624,280 discloses an electrical branch joint box having identical upper and lower casings in which an array of upright sheet bus bars is mounted, with terminals of the bus bars projecting through the casings into connector sockets at the exterior face of the casings. The casings have mutually engageable snap-fit locking components, to lock them together in the assembled condition with the bus bars held between them.
FIGS. 8 and 9 of the drawings illustrate diagrammatically a problem which arises with casings of electrical connection boxes having snap-fit locking components. In FIG. 8, the box 51 has an upper casing 52 and a lower casing 53. Wires and the like are accommodated in each of the upper and lower casings 52,53. Locking projections 54 are formed at the lower edge of the outer side surface of the upper casing 52. At the upper edge of the inner side surface of the lower casing 53, there are locking recesses 55 in which the projections 54 fit. Fitting of the projections 54 in the recesses 55 allows the upper and lower casings 52,53 to be fixedly joined to each other.
However, as shown in FIG. 9, the projection 54 is able to enter the recess 55 owing to its elastic deformation in a direction shown by an arrow F. To allow this reliably, it is necessary to provide a predetermined clearance amount C between the projection 54 and a part of the recess 55. Accordingly, there is looseness or play between the upper casing 52 and the lower casing 53 in correspondence to the length of the clearance C. As a result, due to vibrations generated during travel of a vehicle, the projection 54 and the recess 55 rub against each other to generate abnormal sounds.
In an electrical connection box having vertical bus bars disclosed in Japanese Laid-Open Patent Application No. 7-135717, two casing are joined by fitting them together, as illustrated in FIG. 9, and the resulting looseness between the two casings causes the vertical bus bars accommodated in the box to loosen. Therefore, vibration of the electrical connection box due, for example, to vibration of a vehicle, increases the risk that electrical contacts between tabs of the vertical bus bars and electric components connected to the tabs become defective.
It is an object of the invention to provide an electrical connection box capable of minimizing or preventing looseness between assembled upper and lower casings and looseness of the bus bars included between the upper and lower casings.
According to the invention, there is provided an electrical connection box having an upper casing, a lower casing and mutually engageable locking components on the upper and lower casings for locking the casings together in an assembled condition, the inner sides of the casings defining an interior space when in the assembled condition. A plurality of bus bars are mounted upright in the interior space. At least one of the casings has at least one abutment pressing on the bus bars, when the casings are in the assembled condition and the locking components are engaged, in a manner that maintains the bus bars in desired positions and causes the bus bars to urge the casings apart against the restraint of the locking components.
The abutment or abutments pressing the bus bars are preferably projections or narrow rib-like bars, achieving contact with the bus bars at a small area, in order to provide a pressing force eliminating looseness and play.
In a preferred embodiment the bus bars have main longitudinal body portions of flat shape arranged upright in an array alongside each other and extending parallel to each other in a longitudinal direction, and the box has a plurality of the abutments in the form of longitudinal members each extending across the array of bus bars perpendicularly to the longitudinal direction of the bus bars, the members being spaced apart along the length of the bus bars.
In the invention, the reaction force generated by the engagement of the abutment or abutments and the bus bars urges the upper and lower casings apart. This prevents looseness or play at the locking components even though a clearance is provided between the locking components. The natural resilience and/or flexibility of the material of the casings permits the locking components to engage each other, while also allowing the bus bars to press the casings apart so as to eliminate looseness. Therefore, it is possible to prevent looseness between the upper and lower casings. The engagement force between the upright bus bars and the abutment or abutments thus also acts to prevent the bus bars from being loose in the casings. Thus, the bus bars can be reliably and securely placed at predetermined positions in the casings. The casings are typically made of a suitable electrically insulating plastic material having an inherent slight deformability.
If a plurality of abutments are arranged to act on the bus bars and extend transversely to the bus bar array and are disposed at predetermined intervals over the entire length of the bus bars, the array of bus bars are uniformly pressed in position, and the casings are urged apart in a balanced manner.
Pressure connection blades may be formed on the vertical bus bars so that by pressing an electrical wire against the pressure connection blades of adjacent or spaced bus bars, the bus bars can be electrically connected to each other. Such an arrangement makes it easy to electrically connect the bus bars and to design or alter a bus bar circuit. It is also easy to prevent the electric wire from being separated from the pressure connection blade as the bus bars are prevented from loosening. Accordingly, the reliability of the connection between electrical wires and the bus bars is improved.
The invention extends to use of the electrical connection box in a vehicle, for example, an automobile.
In this specification, including the claims, the directional terms xe2x80x9cupperxe2x80x9d, xe2x80x9clowerxe2x80x9d, etc. are used solely for convenience and clarity of description and definition. It is to be understood that the electrical connection box of the invention can be assembled and used in any orientation.